The present invention relates generally to the field of fuel cell systems and more specifically to fault detection in fuel cell systems.
In a wide variety of applications, fuel cells are used to provide relatively cleaner and higher efficiency electrical power compared to fossil fuel burning electrical power plants. A conventional fuel cell system comprises a fuel cell and a fuel cell controller.
The fuel cell typically comprises a means for bringing a fuel gas, typically hydrogen, and an oxidizer gas, typically air or oxygen, into contact with opposite faces of an electrolyte membrane. Chemical reaction develops a voltage across the membrane, and this voltage can be used to power external electrical devices. Byproducts of the reaction include chemical byproducts, typically water, and heat. Additionally, the fuel cell typically comprises numerous sensors for measuring critical operating parameters of the fuel cell and numerous actuators for modulating the fuel and oxidizer gas flows. The fuel cell controller typically comprises an electronic processor for implementing a nominal control strategy, where the nominal control strategy is an algorithm for calculating gas flow modulation from the measured operating parameters and from a set of desired operating parameters.
The nominal control strategy, however, assumes a normally working fuel cell. When fuel cell partial failures (also called xe2x80x9cfaultsxe2x80x9d) occur, system performance generally tends to degrade. Such performance degradation arises from a combination of at least two causes: diminished fuel cell capability, and mismatch between the nominal control strategy and the dynamic behavior of the partially failed fuel cell. Where the second cause is a significant factor, if it were possible to detect and classify the fault, then it may also be possible to adopt an alternative control strategy tailored to the dynamic behavior of the partially failed fuel cell and thereby recover a portion of the lost performance. An opportunity exists, therefore, to improve the performance of some partially failed fuel cells by detecting fuel cell system faults.
The opportunities described above are addressed, in one embodiment of the present invention, by a method of detecting faults in a fuel cell system, the method comprising: comparing a plurality of fuel cell measurements to respective ones of a plurality of range limits to yield a plurality of range flags; differentiating the fuel cell measurements to yield a plurality of fuel cell rates; comparing the fuel cell rates to respective ones of a plurality of rate limits to yield a plurality of rate flags; and classifying the range flags and the rate flags to yield a fault detection decision.